Ref T773, allow to update CG per model string

* needed if CG is overridden by "dot command"
* update all existing aircraft (in range) if changing CG per modelstring
* made "overriddenCGorDefault" public so it can be checked if overridden
* use overridden value in CContextSimulator::xCtxAddedRemoteAircraftReadyForModelMatching
* allow to clear overridden values

src/blackcore/context/contextsimulatorimpl.h

@@ -181,6 +181,9 @@ namespace BlackCore
             //! Register myself in DBus
             CContextSimulator *registerWithDBus(BlackMisc::CDBusServer *server);
 
+            //! Simulator plugin available?
+            bool isSimulatorPluginAvailable() const;
+
         private:
             static constexpr int MatchingLogMaxModelSetSize  = 250; //!< default value for switching matching log on
             static constexpr int MaxModelAddedFailoverTrials = 3;   //!< if model cannot be added, try again max <n> times